An Overview of Laser-Scan’s Radius Topology 2.5

By
Hal Reid

As the
march continues toward a common data store for geographic and CAD
files, an interesting approach to this challenge is one developed by
UK-based Laser-Scan.Their
approach to the common data store (as embodied in Radius Topology 2.5),
is to insert automation into the maintaining of clean geospatial data.
In addition, Radius Topology uses topology for rapid access to and
highly optimized spatial queries of that data.

The concepts and applications of topology are not trivial, as explained
here by Laser-Scan's definition of topology.

"Topology describes the characteristics of a geometric figure which
are invariant under continuous deformation of the coordinate space.For
example, a Compact Disc is topologically identical to a funnel - just
press the centre of the disk downwards.Calculating properties such as
adjacency, colinearity and containment from geometry is computationally
intensive.Topological data structures allow expensive geometry
comparison algorithms to be re-cast as simple combinatorial (algebraic)
algorithms."

In less complex terms, the use of topology simplifies the access to
complex relationships among disparate geometries.Click here for a
very good white paper on topology and databases.

While databases are now storing geospatial data, either directly as in
Oracle 9i or 10g, or via ESRI's SDE, there is a significant need to
insure that not only the common store is accessible by various parts of
the enterprise using various platforms of GIS and CAD, but that the
data is clean and follows some type of rules-based topology so that
data integrity remains intact.

The rules and mechanisms of the Radius Topology engine insure that
counties do indeed fall within states, polygons connect, and there is
continuity across the road network.If the rules are not in place and
working as designed, then the accuracy and usability of the common
store is compromised, potentially making the use of the common store
questionable.

In Business GIS, there has always been the "dream" of tying store or
plant locations to the drawing files that were used to create those
stores or plants in the first place - but it's never quite come to
fruition.That would constitute a sub-geography within the overall
physical geography.This could be used for facility maintenance,
property meets and bounds descriptions and a whole series of plans,
drawings and specifications on the why and how of a particular
location.The logic is to find the location on a map (electronic, not
paper) and then drill down to the files related to that location.But
in order to do so, GIS, CAD and IT have to come together.This is where
Radius Topology comes in.

In contrast to business, local governments have been linking CAD and
GIS into a common store for some time because a major part of their
role is knowing where things are.Typical items like what's inside the
streets, the jurisdictional area extents and what makes up all the
basic infrastructure that is the core of a community.Homeland security
has also pushed local governments to adopt the concepts of being able
to locate things in a central data store and having information about
them immediately at hand.In some cases, these common stores are
directly accessed by both the public and private sectors.

Click image for larger view.

We recently ran an article about this type
of CAD and GIS common storage at the Las
Vegas Valley Water District.The bottom line for the Water District
was that they could have the detail and accuracy of CAD within their
GIS, because they could use the same data, and anything updated in a
CAD file was immediately available to GIS users.

Laser-Scan has taken the common store concept a step farther by
incorporating two key features:

Data cleansing and topology
corrections on the fly, from both CAD and GIS files, as the data is
placed in the common store in Oracle.

Faster spatial queries, because the
queries can be more precise in their scope.

Another feature is the ability to use
tables created either with Oracle or via Radius Topology.This means
that if you already are using Oracle for your geospatial data store,
the transition to using Radius Topology is relatively seamless.

When considering using any software that is designed to work with
several other platforms, the question I always have to ask is, "How
much of an issue is it to get this software to work with what I have in
place?" Radius Topology states that they seamless integrate with
Autodesk, Intergraph, MapInfo and STAR Informatic GIS products.No
modifications, no plug-ins, it just works transparently.Radius
Topology is presented by Laser-Scan as the "Universal Component" for
common data storage in Oracle.

Other advantages are that everything is working on the server side,
therefore allowing for very thin clients.Like all software of this
scope, it also has to be very scalable - what starts out as a good idea
and initially works doesn't quickly become eclipsed by the volume of
users or the number of transactions.

Radius Topology uses these Oracles features:

Native support of spatial data types

Spatial indexing.

Data stored in a table (conceptually) goes
from this...(from a paper by Paul Watson prepared for Laser-Scan,
January 2002).

Click image for
larger view.

...to this....

This way, users can take advantage of all the standard database
features of table joins and queries, linking, etc.The Radius Topology
claim to fame is that the data will be clean, polygons will close and
linear features will go from beginning to end.

If you want to bring several departments together into a common data
store and are now using Oracle 9i or later, it would appear to be worth
a conversation with Laser-Scan about this product.